Class 6: Suprachiasmatic Nucleus: The Central Clock

Vocabulary flashcards covering the key terms and concepts of the suprachiasmatic nucleus as the central clock.

Suprachiasmatic nucleus (SCN)

The brain structure identified as the central clock and core pacemaker governing circadian rhythms.

Properties of a central clock

include synchronization of physiological processes, regulation of sleep-wake cycles, and response to light cues.

Retinohypothalamic tract

A neural pathway whose disruption in lesion studies impacts circadian rhythms of hormone release and behavior.

Central clock

The core circadian pacemaker, identified as the SCN, which coordinates and maintains relationships with clocks in peripheral tissues.

What can a lesion of the retinohypothalamic tract cause (in a circadian rhythm)?

This can prevent the SCN from receiving light information, disrupting the synchronization of circadian rhythms; also since the brain can never adapt to environmental light changes, leading to irregular sleep-wake cycles.

What can a lesion of the hypothalamus cause (in a circadian rhythm)?

Normal 24-hour peaks and troughs of hormone secretion (such as melatonin and corticosterone/cortisol) are flattened or lost. Daily patterns such as the sleep-wake cycle, feeding schedules, and locomotor activity become arrhythmic and fragmented across the 24-hour period rather than synchronized to day and night.

What can a lesion of the SCN cause (in a circadian rhythm)?

Can cause complete arrhythmic, flattened endocrine cycles, and melatonin/cortisol release is completely destroyed.

Electrophysiology

A technique used to measure neuronal activity and electrical activity rhythms in specific parts of the brain, including SCN neurons.

Cell-autonomous rhythmic activity

The independent electrical activity rhythms observed in SCN neurons, evidenced by recordings from isolated SCN neurons in living rats and from explanted SCN neurons in a dish.

Tau mutant hamster transplant studies

Because the recipient hamsters adopted the specific period phenotype of the donor SCN, this experiment conclusively proved that the SCN contains the autonomous, intrinsic timing mechanism that sets the pace for the entire organism.

SCN core and shell regions

Anatomical subdivisions of the suprachiasmatic nucleus characterized by anatomical differences and the expression of distinct neuropeptides.

SCN and clock relationship in peripheral tissues

The relationship highlights how the suprachiasmatic nucleus (SCN) regulates circadian rhythms in peripheral tissues, synchronizing their biological functions with the central clock's timing signals. The SCN serves as the master clock, influencing gene expression and metabolic processes in peripheral tissues to maintain circadian harmony within the body.